(A) Field of the Invention
The present invention relates to a low temperature probing apparatus, and more particularly, to a low temperature probing apparatus using a hydraulic stage to retain the probe unit holding the probes or probe card.
(B) Description of the Related Art
Integrated circuit devices have become the necessary core of every electronic device. This includes the vehicle-control system in the automobile running on the road or at zero degrees Celsius, or the communication system in the airplane flying in the sky in subzero temperatures. The integrated circuit devices inside these electronic systems must operate normally without failing due to the dramatic temperature variation. To verify and qualify whether the integrated circuit devices can operate normally under such low temperatures, the integrated circuit devices have to be tested in an environment under such conditions or at even lower temperature.
Generally, it is necessary to test the electrical characteristics of integrated circuit devices on the wafer level to verify the performance of the integrated circuit device and to satisfies the product specification. Integrated circuit devices with electrical characteristics satisfying the specification will be selected for the subsequent packaging process, and the other devices will be discarded to avoid additional packaging cost. Another electrical property test will be performed on the integrated circuit device after the packaging process is completed to screen out the below-standard devices to increase the product yield. In other words, the integrated circuit devices must undergo several electrical tests during the manufacturing process.
Currently, the method used in the testing of integrated circuit devices includes setting the positions of the device under test and the testing tools prior to isolating the testing room from the environment and using liquid nitrogen to cool the testing room down to the desired testing temperature, and performing the low temperature testing. During the testing, the operator has to move the device or the probe card and manipulator such that the probe of the probe card can contact different devices or different pads of the same device.
However, moving the probe card and the manipulator cannot be achieved until the isolated testing environment is exposed to the surroundings, and exposing the isolated test environment results in the communication of the low-temperature environment with the higher-temperature environment such that moisture condenses into water droplets, influencing actual temperature of the devices under test and also the damages the cooling mechanism that tries to lower the temperature below freezing temperature. The condensed water droplets or ice can further cause a short circuit if it contacts the circuit of the testing tools. In addition, after the test environment is isolated again, the temperature will drop further causing poor contact of the probes on the wafer as the probes skids away from the contact area when the wafer further shrinks from lower temperature.
To solve this problem, researchers try to avoid the opening of the testing room by using the electrical stage instead of the manipulator. However, using the electrical stage to retain the probe or the probe card results in closing of the electrical stage to the device under test or the probe card, and the electromagnetic noise generated from the operation of the electrical stage deeply influences the accuracy of the testing result. Consequently, the use of the electrical stage instead of the manipulator is not feasible. In addition, electrical stage requires electrical power and external control software which may not be feasible in a manual station.
U.S. Pat. No. 6,257,319 discloses an IC testing apparatus for performing a test by applying at least a low temperature stress to ICs to be tested comprising a refrigerant cycle wherein at least a compressor, condenser, expansion valve and evaporator are connected in order, and a cold air applying line having a blower for supplying heat exchanged cold air by the evaporator to the ICs to be tested. However, U.S. Pat. No. 6,257,319 only teaches how to generate the low temperature testing atmosphere, and does not disclose the solution for the above-mentioned problem.